使用Winston-Lutz测试进行辐射等中心的高精度定位：准直器角度、幻像位置和视场大小的影响。

IF 2.2 4区医学 Q3 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING Journal of Applied Clinical Medical Physics Pub Date : 2025-02-04 DOI:10.1002/acm2.70000

Weiliang Du

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引用次数: 0

摘要

目的：本研究旨在评估准直器角度、球轴承（BB）幻像位置和视场大小对温斯顿-卢茨（WL）测试所得辐射等中心精度的影响。方法：对4台TrueBeam直线加速器进行WL试验。每个WL测试获得56张图像（8个龙门角度乘以7个准直器角度）。采用不同准直角度的图像计算辐射等心。所得的辐射等中心与准直器角度相关。然后，在随后的WL试验中，改变BB位置和辐射场大小。将计算得到的BB偏移量与已知偏移量进行了比较，并比较了不同场尺寸下的辐射等中心。结果：使用单一准直角度导致计算的辐射等心误差高达0.4 mm。在准直角为0°和90°和/或270°时得到的辐射等心之间存在系统差异。通常使用的反向准直角对，90°和270°，导致辐射等心向天花板垂直偏移0.1毫米。斜对或混合准直角度产生的辐射等心误差小于0.1毫米。WL试验得出的BB位移与已知位移相差小于0.1 mm。在2 × 2 cm2到20 × 20 cm2范围内，辐射等中心的变化小于0.1 mm。结论：应考虑斜对准直器角度对，以尽量减少定位辐射等中心的误差。如果将BB用作空间中的静态参考点，则可以消除BB定位中的不确定性。磁场大小对辐射等中心无显著影响。通过仔细设计WL测试参数和图像处理，可以在使用WL测试定位辐射等中心时达到0.1 mm的精度。

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High-precision localization of radiation isocenter using Winston-Lutz test: Impact of collimator angle, phantom position, and field size

Purpose

This study aimed to evaluate the impact of collimator angle, ball bearing (BB) phantom position, and field size on the accuracy of Winston-Lutz (WL) test–derived radiation isocenters.

Methods

WL tests were performed on four TrueBeam linear accelerators. Fifty-six images (eight gantry angles multiplied by seven collimator angles) were acquired for each WL test. Images with different sets of collimator angles were used to compute the radiation isocenters. The resulting radiation isocenters were correlated with the collimator angles. Then, the BB position and radiation field size were varied for the subsequent WL tests. The calculated BB shifts were compared with the known shifts, and the radiation isocenters were compared between different field sizes.

Results

The use of a single collimator angle led to errors of as much as 0.4 mm in the calculated radiation isocenters. Systematic differences were observed between the radiation isocenters derived with collimator angle 0° and those derived with 90° and/or 270°. A commonly used opposing collimator angle pair, 90° and 270°, resulted in a vertical 0.1 mm offset of the radiation isocenters toward the ceiling. Oblique opposite or mixed collimator angles yielded radiation isocenter errors less than 0.1 mm. The BB shifts derived from WL tests were less than 0.1 mm from the known shifts. The radiation isocenters varied by less than 0.1 mm between field sizes ranging from 2 × 2 cm² to 20 × 20 cm².

Conclusions

Oblique opposing collimator angle pairs should be considered to minimize errors in localizing radiation isocenters. Uncertainty in BB positioning could be eliminated if the BB is used as a static reference point in space. The field size had no significant effect on the radiation isocenters. With careful design of WL test parameters and image processing, it is possible to achieve a precision of 0.1 mm in localizing radiation isocenters using WL tests.

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来源期刊

Journal of Applied Clinical Medical Physics 医学-核医学

CiteScore

3.60

自引率

19.00%

发文量

331

审稿时长

3 months

期刊介绍： Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission. JACMP will publish: -Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500. -Review Articles: Reviews of major areas or sub-areas in the field of clinical medical physics. These articles may be of any length and are peer reviewed. -Technical Notes: These should be no longer than 3000 words, including key references. -Letters to the Editor: Comments on papers published in JACMP or on any other matters of interest to clinical medical physics. These should not be more than 1250 (including the literature) and their publication is only based on the decision of the editor, who occasionally asks experts on the merit of the contents. -Book Reviews: The editorial office solicits Book Reviews. -Announcements of Forthcoming Meetings: The Editor may provide notice of forthcoming meetings, course offerings, and other events relevant to clinical medical physics. -Parallel Opposed Editorial: We welcome topics relevant to clinical practice and medical physics profession. The contents can be controversial debate or opposed aspects of an issue. One author argues for the position and the other against. Each side of the debate contains an opening statement up to 800 words, followed by a rebuttal up to 500 words. Readers interested in participating in this series should contact the moderator with a proposed title and a short description of the topic